Differential meter



Jan. 16, 1934. E. P. ST EWART ET AL 1,943,993

DIFFERENTIAL METER Original Filed May 9, 1931 rill-m EarlIllfza/vesrfwAkr' [00/5 h. FA05T A; ATTORNEY Patented Jan. 16, 1934UNITED STATES DIFFERENTIAL METER Elon P. Stewart, Syracuse, N. Y., andLouis H.

Frost, Cleveland, Ohio, assignors to Cement- Gun Company, Inc., acorporation of New York Original application May 9, 1931, Serial No.

536,233. Divided and this application September 10, 1932. SerialNo.632,510

2 Claims.

The present invention relates to differential meters and moreparticularly to a differential meter or gauge adapted to be operated bythe varying pressure drop produced by suitable means, such as a diskorifice, inserted in a fiow stream of fluid, which may be air. Thisapplication is a division of our copending application Serial No.536,233, filed May 9, 1931. portant object of the invention is toprovide an improved meter or gauge of the general class specified.Another important object of the invention relates to the provision of animproved gauge in which an index is moved proportionally to changes inflow- One of the features of the invention relates to the provision of aconnection whereby an index is moved substantially in accordance withthe proper velocity square root function of the differences of pressureinstead of movement directly in' accordance with the differences inpressure. In other words, according to this feature equal changes ofvelocity in the flow stream produce equal changes in the movement of theindex. Other features relate to vari ous features of construction andarrangement.

In carrying out the invention in accordance with a preferred embodimentthereof, provision is made of a casing including a high pressure portionin the general form of .a dome, connected at its substantially circularopen end with a low pressure portion having a corresponding open end.The plane of said openings is preferably vertical and the low pressurepart of the casing is arranged with a vertical wall extending downwardly from said opening therein and a wall arranged in the arc of acircle from the lower part of said vertical wall to the top of thecasing, in order to accommodate a weighted arm swinging about a fixedpivot in this casing section. Preferably the weighted arm is provided ata point below its pivot and in such angular relation with the axis ofthe weighted arm that when connected by a link of suitable length with areciprocating rod secured in a piston or the like between said chambers,the movement of the rod by differential pressures in the two sections ofthe casing will cause the rod to move approximately in accordance withthe velocity square root function of the differences in pressure.Preferably also, the end of the rod in the high pressure chamber isguided in an opening in a screw plug extending through the casing andalso serving as a stop for the reciprocating rod. Preferably also theefiective length of the weighted arm may be varied.

Other objects and advantages will appear upon An im-v consideration ofthe following description and of the drawing, in which Fig. 1illustrates the differential meter in elevation, showing it connected toa pipe containing a pressure differenoeproducing aperture;

Fig. 2 is a sectiontaken on the line 22 of Fig. 3, and

Fig. 3 is an elevation of the measuring device, viewed from the right inFig. 1.

Referring to the drawings, a pipe or hose 20 is provided with a valve 22to control the passage of fiuid therethrough, and with a suitableorifice in the form of a thin segmental plate 28 projecting into thepipe. The ilow of fluid, such as air, past the segmental orifice createsa differential pressure between the spaces at opposite sides of theorifice. This differential pressure bears a fixed relation to thequantity of air, or other fluid, passing through the orifice.

Thisdifierence in pressure is utilized to operate a suitable instrumentor meter 29 which is connected by suitable ducts 30 and 31 with the pipe20 at the high pressure and low pressure sides respectively of thesegmental orifice formed at the segmental plate 23. The duct 30, whichmay be in the form of aflexible hose, is connected with a section orportion 32 of the device 29 so as to communicate with the interiorthereof, and the duct 31, which also may be in the form of a flexiblehose or tube, is connected with the interior of a casing member 33 alsoforming a part of the device 29. f

The portion 32 of the casing 39 maybe in the general form of a domeconnected at its substantially circular open end with a correspondingopening in the casing member 33. Projecting through the dome-likeportion 32 and parallel to the plane of division of the casing members32 and 33, is a shaft 34 carrying at one end an index or pointer 35 tocooperate with a suitably calibrated scale 36 on a member or disc '37through which the shaft 34 passes. Leakage of air where the shaft 34projects from the casing may be prevented in any suitable manner. Thedisc 3'? may be supported from the main body of the device 29 in anysuitable manner asby means of bars 38 (Fig. 3). To operate the pointer35 use is made of a rod 39 mounted for reciprocation axially of thedome-like member 32. At one side the rod 39 is provided with teeth 40forming a rack to cooperate with the pinion 41 mounted on the shaft 34which carries the index 35.

The rod 39 is moved longitudinally by differences in pressure at theinterior of the easing members or sections 32 and 33 and to this endpasses centrally through a diaphragm 42 of suitable material, such asrubber, clamped between adjacent portions of the casing members 32 and33 by suitable means including bolts 43 passing through a flange 44 onthe dome-like member 32 and corresponding portions of the casing member33. The diaphragm 42 is supported at opposite sides by the pistons orpiston members 45 and 46 which fit loosely enough in the opening betweenthe casing sections to permit the rubber diaphragm to fold between thepiston members and adjacent walls of the two casing members 32 and 33.Thepiston members 45 and 46 are held in position on the rod 39 by anysuitable means such as members 4'? and 48 fixed on the rod 39. Onopposite sides of the diaphragm 42 the casing members 32 and 33 areprovided with stops 49 and 50, respectively, preferably in the form ofrings.

At the center of the dome-like member 32 it is provided with a bore 51into which is threaded a screw plug 52 provided at its interior with abore 53 which extends to its inner end and receives the correspondingend of the rod 39 for guiding purposes. The inner end of the bore 53 mayalso serve as a stop to limit the movement of the rod 39 in thatdirection under urging of the weight 55 removably and adjustably securedon arms 56 by means including a nut 57 screwed on a projection 58connected with said arms 56. The arms 56 are on the opposite sides ofthe rod 39 and are pivoted on a shaft 59 above the rod 39 and mounted inbearings 60 projecting inwardly from opposite sides of the casing member33. Each arm 56 is flat and in the form of a bent lever having a portion61 extending below the rod 39 and pivoted at 62 to a link 63 which inturn is pivoted at 64 to the rod 39. By inspection of Figs. 1 and 3, itwill be seen that the weight 55 tends to turn the pointer 35 back to thezero reading where the rod 39 may be stopped by engagement with thebottom of the bore 53 in the screw plug 52. Preferably the casingsection 33 is shaped to correspond with the swinging movement of theweight 55 on the arms 56. In its reciprocation the rod39 is guided atone end in the screw plug 52 and at its other end in the bearing 64a.

At its lower part the casing section 33 may be provided with a bore 65normally closed by a screw plug 66 to enable adjustment of the weight 55by means of the nut, the arrangement being such that the weight 55 mayassume a position with the nut 57 immediately above the bore 65.

If the valve 22 in the air line 20 is closed, there will be no flow ofair through the pipe and consequently no differences in pressure atopposite sides of the plate 28. Under these conditions the weight willswing downwardly to bring the nut 5'? immediately above the bore 65, theexact position being determined by engagement of the left end of the rod39 (Fig. 2) with the end of the bore in the screw plug 52. At this timethe pointer 35 should be positioned at the zero indication of the scale36. At the time that the piston member 45 is in engagement with the stopring 49, the portion of the diaphragm 42 extending from the pistonmembers 45 and 46 to the diaphragm clamping portions of the casingsections 32 and 33 will be straightened out and stretched to its limit.Upon opening the valve 22 the air will begin to fiow through the supplypipe 20 and there will be differences of pressure at the opposite sidesof the thin plate 28 at the measuring aperture. The pressure transmittedthrough the line 30 will be greater than that transmitted through theline 31 and consequently the piston members 45 and 46 will be forced tothe right against the action of the weight 55 thus causing the pointer35 to move away from the zero reading of the scale 36. If thedifferences in pressure are sufficiently great, the rod 39 will beforced to the right (Fig. 2) until the right hand piston member 46 comesinto engagement with the stop or stop ring 50.

The difference in pressures at opposite sides of the thin plate orificebears a fixed relation to the quantity of air passing through theorifice. The quantity of air passing through the orifice is directlyrelated to the velocity of the air current and the difference inpressure is such a function of the velocity that uniform changes ofvelocity would cause changes of pressure differences which were notuniform. However, the link motion between the weight 55 and thereciprocating rod 39 is so designed as to transform square root velocityrelation which would ordinarily produce unequal divisions of the scale,substantially into graduations of uniform length, as illustrated inFig. 1. Such designing may be Worked out in any suitable manner, as forexample, by the use of graphic methods. As used in said copendingapplication the scale 36 on the disk 37 was calibrated to read directlyvelocities at the nozzle of the cement gun or the like in suitableunits, and if nozzles were changed, the scales were changed. When usedfor other purposes the scales may be calibrated to read directlyvelocities in the air duct or pipe 20.

It should be understood that the differential meter 29 is also adaptedfor use with flows, velocities and pressures encountered in use withPitot measurements, rods and other flow measuring devices. For this use,however, the meter would preferably be larger than that required for usewith the cement gun.

It should be understood that the apparatus may be changed in variousways and that certain features may be used without others withoutdeparting from the true spirit and scope of the invention.

Having thus described our invention, we claim:-

1. In a device of the character described, two casings having verticallydisposed circular openings adapted to register with each other andcoaxial inner cylindrical surfaces extending away from the plane of saidopenings between said casings, each of said casings having an inlet toadmit fluid thereto so that one casing is a higher pressure casing andthe other casing is a lower pressure casing, a piston arranged toreciprocate within said cylindrical surfaces, an annular diaphragmextending from said piston and clamped between said casings at saidcircular openings, a substantially horizontal rod secured in said pistonand projecting therefrom into and substantially across the higherpressure casing, means for urging the rod toward the side of the higherpressure casing away from the lower pressure casing, including in thelower pressure casing a weighted lever pivoted above said rod and a linkpivoted to said rod and to said lever beneath the pivot of the lever,means in the higher pressure casing for limiting the movement of the endof the rod in the higher pressure chamber and indicating means having arack and pinion connection with said rod.

2. In a device of the character described, two

casings having a substantially horizontally dis posed passagetherebetween and each of said of said chambers, indicating meansconnected with said rod to move directly in accordance therewith, aweighted arm in the low pressure chamber pivoted above said rod and alink pivoted to said rod and to said lever beneath the pivot of the arm.

ELON P. STEWART. LOUIS H. FROST.

